Xerographic powder fixing apparatus



Jan 26, 1960 c. F. CARLSON XEROGRAPHIC POWDER FIXING APPARATUS Original Filed July 18, 1952 zzf anni).

l, H INVENTOR. u CHESEER F. CARLSON BY I ATTO/PNE United States Patent() 2,922,230 XEROGRAPHIC POWDER FIXING APPARATUS Chester F. Carlson, Pittsford,.N.Y., assignor, by mesne assignments, to Haloid Xerox Inc., Rochester, N.Y., a corporation of New York Original application July 18, 1952, Serial No. 299,673. Divided and this application December 119, 1955, Serial No. `554,006

11 claims. (CLM- 151) This invention relates to image fixing apparatus, particularly apparatus for fixing Xerographic powder images.

The present application is a division of co-pending application, Serial No. 299,673, filed July 18, 1952, now Patent No. 2,776,907, granted January 8, 1957.

IIn certain electrostatic recording processes, such as the electrophotographic, Xerographic and electric printing processes described in my Patents 2,221,776, 2,297,691 and 2,357,809, and the process of graphic recording described in my Patent 2,624,652, issued January 6,1953, an electrostatic image is developed by depositing a powder on a surface to produce a powder image. The powder image is then aixed to the surface upon which it has been deposited or on another surface to which it has been transferred. Heretofore, the usual method of fixing has been by the process of heat fusing, in which case the powder image must be formed of a thermoadhesive material, such as a fusible resin, which becomes adhesive when heated.

VWhile heat fusing has been put to practical use, certain difficulties have been encountered. Where the image is to be fused to paper or other organic base, as is usually the case, the powder must be made of material which becomes adhesive at a temperature below that which will cause damage to the organic base. This imposes limitations on the choice of resins which make it difficult to meet other desirable characteristics in the powder composition. Moreover, it has been difficult to reach an entirely satisfactory design of heat fuser with regard to short warm-up time, low electric current requirements, adequate heat insulation and uniform heat distribution.

Fixing of powder images by condensing a liquid solvent onto Vthe image surface from a heated solvent vapor, as described, for example, in my above-mentioned Patent 2,624,652 and in my co-pending application Serial No. 157,883, filed April 25, 1950, has been successfully used and offers the advantages of a broadened choice of powder materials, lower power requirements, and elimination of heat damage to the base sheet.

The present invention contemplates a further improvement in solvent vapor fixing of powder images which eliminates all electric power requirements, simplifies the design of equipment, materially reduces the consumption of solvent and the loss of solvent vapor, and eliminates all delays due towarmup time. This is accomplished by apparatus in which the powder image is introduced into an atmosphere of solvent vapor which is at substantially the same temperature as the powder image, or even at a lower temperature than the image. The vapor atmosphere is held at a vapor concentration sufficient to produce absorption of solvent vapor by the powder image and consequent fusing of the image, but there is no thermal condensation on the paper or other base which supports the powder image. The base material consequently remains dry. Y

Other features of the invention will be brought out and exemplified inthe disclosure hereinafter set forth, -including the illustrations in the drawings.4

fi ice In the drawings:

IFigure 1 illustrates a manually operated cold vapor fixing device for iixing powder images onto sheet materials according to the present invention; and

Figure 2 is a section on the line 2-2 of Figure 1.

The vapor xing device of Figures 1 and 2 is a hand operated unit which may be used for fixing powder images onto individual sheets of paper, cloth, metal, plastic or the like, and even onto the surfaces of electrophotographic plates. It comprises a wooden box or housing 10 forming a -wide flat and deep enclosure having its mouth or entrance at one end. A pair of triangular legs 11 support the housing at an incline of about 30 degrees with the horizontal supporting surface, the mouth forming a horizontal opening at the upper front end.

The housing 10 is lined with a sheet metal lining 12 which is welded or soldered to provide a liquid-tight vapor chamber 13. The open end of lining 12 projects a short distance out of the mouth of wood housing 1t), as shown at 14, the sheet metal being doubled back and bent out to provide flanges 1S which fit against the end of the wood housing andwhich may be attached to the wood housing. A slide member 16 of sheet metal is arranged to be moved into and out of vapor chamber 13 by its wooden end piece 17 which is provided with a handle 18. End piece' 17 is provided with a groove which ts over the projecting edges 14 of the lining 12, so that when the slide is inserted in the chamber the'block 17 provides a tight closure for the vapor chamber. Slide 16 rests flat against the sloping lower wall of the chamber and is turned up and back at its inner end to provide a channel portion 19 in which the lower end of a copy sheet carrying a powder image may be inserted for positioning and support during fixing.

A solvent wick 20 formed of felt, cloth or blotting paper is supported against the sloping ceiling of the vapor chamber 13 by a series of stiff sheet metal ribs 21 which are secured at their outer ends to the ceiling near the mouth of the chamber and extend along close to the ceiling and then bend down to form feet which rest on the bottom and bear against the rear end of the chamber. The lower end of wick 20 is rolled into a wad 22 at the bottom of the chamber.

The fixing device is prepared for operation by pouring a quantity of a liquid solvent into. the chamber suicient to saturate the Vwick 20. The slide is inserted so that the end piece 17 closes the chamber and the device is allowed to stand until the solvent is drawn up along the ceiling of the chamber by the wick and the vapor space 13 becomes saturated with solvent vapor. The choice of solvent will depend upon the composition of the powder images to be fixed. With powders formed of pigmented rosin, copal, asphalt and other natural resins as well'as several synthetic resins and plastics, such as ethyl cellulose, a desirable solvent is trichlorethylene. Amyl acetate or butyl acetate can likewise be used with many resins. Butyl alcohol and perchlorethylene are also useful, particularly in hot weather, as they are somewhat less volatile.

Powder images can be fused in the device asgsoon as a saturated Vvapor atmosphere has been generated. Once the wick has become wet with solvent over its entire area the necessary vapor atmosphere is quickly produced. The operator can then fix copies by simply grasping handle 18, withdrawing slide 16, placing a sheet bearing a'powder image on the slide, inserting the slide in the chamber 13 for a few seconds, withdrawing the slide and removing the -copy.

Although the solvent and solvent vapor are at the same temperature as the copy sheet and powder image,

powder absorbs solvent from the vapor phase until it becomes adhesive. In some instances the powder image will absorb enough solvent to completely liquefy it. It has been found, however, that serious spreading of the image does not take place on paper base material unless the copy is allowed to remain in the fixing device much longer than the few seconds needed for fusing. The fusing time is not critical, whereas it is with heat fusing.

As soon as the fused copy is removed from the vapor chamber the solvent begins to evaporate fro-m the image and the image solidies and becomes permanently bonded or fixed onto the base material in a few seconds.

Since the solvent vapor has a density greater than that of air it tends to remain in the vapor space 13 as the slide is removed and reinserted. The small loss of vapor due to absorption by the powder image and drag-out by the slide is quickly regenerated from the wick so that copies can be fused in rapid succession. On the other hand, when not in demand, the device stands ready for use at any moment since the vapor atmosphere is maintained in the space 13 at all times. Recharging with solvent is necessary only at infrequent intervals and with moderate use one charge of a few cubic centimeters of liquid solvent may last several days.

This method of operation, in which the vapor is at the same temperature as the copy, is much more economical of solvent than vapor xing methods in which the solvent is heated, as with cold vapor there is no condensation on the paper base unless it carries a resin or material soluble in the solvent used. In most cases the powder image is the only part of the copy which absorbs the solvent and its requirements are very small. With unheated solvent the loss due to vapor leakage from openings in the vapor space is practically negligible since the vapor is kept denser than air and no vapor pressure is built up to drive solvent out of the chamber.

The advantages of the present invention are most fully realized in lthe xing of powder images to paper using the vapor of a non-aqueous solvent such as the organic solvents and chlorinated organic solvents, where the economy of solvent consumption is an important factor, and the evaporation of excessive quantities of solvent into the room may be objectionable. Moreover, these solvent vapors at the same temperature as the copy to be fixed are not noticeably absorbed by the paper base and do not produce any dimensional change or buckling in the base.

Aqueous solvents are not useful, of course, in fixing most resin or plastic images as these materials are not water-soluble. Where water-soluble image forming materials are used, some spreading and loss of sharpness may frequently take place due to the humidification of the cellulose fibres of the paper during fusing.

For effective fusing of a powder image to take place the solvent vapor is held at a great enough concentration in the vapor fixing chamber to produce absorption of solvent vapor by the powder until the powder becomes adhesive. This means that the partial pressure of the solvent vapor shall exceed the vapor pressure of a solution of the powder (or the soluble constituents of the powder) which contains sufficient absorbed solvent to be adhesive. A concentrated vapor atmosphere is insured by providing a resorvoir of liquid solvent in contact with the vapor space, particularly if the solvent is brought to the upper part of the vapor space by a wick or other means so that the higher density vapor will settle {and fill the space. The air in the chamber is thus saturated with vapor, and the concentration is maintained in excess of the minimum requirements even with frequent use.

While the advantages of the process are greatest where base materials, such as paper, which are not soluble in the solvent are used, the method may sometimes be used to atiix powder images to plastic lms and to plastic coated paper, in which the plastic may be made adhesive by the solvent and the powder may or may not be affected by the solvent. In the case of films, the fusing time must, of course, be controlled to obtain only a surface adhesion without undue softening of the entire plastic layer.

While the present invention, as to its objects and advantages, has been described herein as carried out in a specific embodiment thereof, it is not desired to be limited thereby, but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

l. Apparatus for fixing a powder image to the surface of sheet material, said apparatus comprising walls deiining a vapor chamber having an Vopening slot in an upper portion thereof, means for introducing sheet material carrying a powder image into said chamber through said slot, the lower part of said chamber providing a reservoir for liquid solvent, and means communicating with the lower part of said chamber and extending upwardly therefrom to produce a ow of liquid solvent through the chamber substantially to the upper portion thereof and to generate solvent vapor from said liquid solvent and introduce said vapor throughout said chamber.

2. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for fixing the powder image to the sheet material comprising a liquidtight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the `bottom of the container when inserted therein, a cover for the container opening fixed on the trailing edge of the slide member, a grid-like structure secured in spaced relation to the inner surface of the top of the container, and a wick-like material supported by the grid structure for containing a solvent for the soluble component of the xerographic image powder material.

3. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for fixing the powder image to the sheet material comprising a boxlike liquid-tight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, a cover for the container opening fixed on the trailing edge of the slide member, a grid-like structure secured in spaced relation to the inner surface of the top of the container, a wick-like material supported by the grid structure, and a solvent for the soluble component of the xerographic image powder material contained in said wick-like material.

4. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for fixing the powder image to the sheet material comprising a box-like liquid-tight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, sheet material retaining means formedV on the leading edge of the slide member, a cover for the container opening fixed on the trailing edge of the slide'member, a grid-like structure 'secured in spaced relation to the inner surface of the top of the container, a wick-like material supported by the grid structure, and a solvent for the soluble component of the xerographic image powder material contained in said wick-like material.

5. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for iixing the powder image to the sheet material comprising a box-like liquid-tight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, sheet material retaining means formed on Ithe leading edge of the slide member, a cover for the container opening lixed on the trailing edge of the slide member, a grid-like structure secured in spaced relation to the inner surface of the top of the container, a wick-like element substantially coterminous with the top wall supported by the grid structure, and a solvent for the soluble component of the xerographic image powder material contained in said wick-like element.

6. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for xing the powder image to the sheet material comprising a box-like liquid-tight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, sheet material retaining means formed on the leading edge of the slide member, a cover for the container opening fixed on the trailing edge of the slide member, a grid-like structure secured in spaced relation to the inner surface of the top of the container, a wick-like material substantially coterminous with the top wall supported by the grid structure and extending in a roll adjacent the rear wall of the container, and a solvent for the soluble component of the xerographic image powder material contained in said wick-like material.

7. In the process of Xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for fixing the powder image to the sheet material comprising a box-like liquid-tight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a planar slide member for supporting sheet material, said slide member lbeing movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, sheet material retaining means formed on the leading edge of the slide member,'a cover for the container opening fixed on the trailing edge of the slide member, said cover having a continuous groove mating with the edges of the top, bottom and side walls of the container, a gridlike structure secured in spaced relation to the inner surface of the top of the container, a wick-like material subgrid structure and extending in a roll adjacent the rear wall of the container, and a solvent for the soluble component of the xerographic image powder material contained in said wick-like material.

8. In the process of xerography wherein a xerographic powder image is formed on the surface of sheet material and wherein the material comprising the powder image includes a soluble component, an apparatus for fixing the powder image to the sheet material comprising a liquidtight container, said container including top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at :an incline to the horizontal with its open end uppermost, a slide member for supporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest near the bottom of the container when inserted therein, a cover for the container opening xed on the trailing edge of the slide member, and a wick-like material supported against the inner surface of the top of said container for containing a solvent for the soluble component of the xerographic image powder material, said wick-like material extending from the rear wall of said chamber to a point adjacent said container opening.

9. Fixing apparatus for afxing powder images to sheet material, comprising a rectangular liquid-tight container having top, bottom, side and rear walls and having an open front end, said side and rear walls being substantially narrower than said t'op and bottom walls whereby said container provides a llat chamber volume, a base having foot surfaces for resting on a horizontal surface, said' container being attached to said base in an inclined position relative to said foot surfaces whereby said rear wall is substantially lower than said open front end when said base rests on a horizontal surface, a removable closure piece for the open front end of said chamber, a handle on the outside of said closure piece and a sliding tray member attached to the inside thereof and extending into said chamber adjacent to the bottom wall thereof when said closure piece is in position against said open front end, a wick extending substantially from the bottom of said container at said rear wall along the inside of the top wall of said container to a position substantially adjacent to the open end thereof, said wick covering substantially the entire Width of said top wall, and means supporting said wick in position.

10. Apparatus for fixing a powder image to the surface of sheet material, said apparatus comprising walls delining a vapor chamber having an opening slot in an upper portion thereof, sheet holding means for introducing sheet material carrying a powder image into said chamber through said slot, the lower part of said chamber providing a reservoir for liquid solvent, and means communicating with the lower part of said chamber and extending upwardly therefrom to produce a flow of liquid solvent through the chamber substantially to the upper portion thereof and to generate solvent vapor from said liquid solvent and introduce said vapor throughout said chamber.

11. An apparatus for fixing a powder image to sheet material wherein the material comprising the powder image includes `a soluble component, said apparatus including a liquid-tight container having top, bottom, side and rear walls, and having an opening at its front end, means for supporting the container at an angle to the horizontal with its open end uppermost, a slide member for Isupporting sheet material, said slide member being movable into and out of the open end of the container within the walls thereof and adapted to rest on the bottom of the container when inserted therein, a cover member for enclosing the container opening when the slide member is inserted into the container, and means within the lower portion of the container and extending upwardly therefrom for producing a flow of liquid solvent throughy7 8 out the chamber substantially to the open end thereof and 557,043 Adams Mar. 24, 1896 for generating therefrom a solvent vapor for the soluble 2,138,578 Hershberger Nov. 29, 1938 component of thepowder image material. 2,282,15 8 Bennett et al May 5, 1942 Y 2,363,715 Wells Nov. 28, 1944 References Cited in the file of this patent 5 2,368,124 Euiott Jam 30, 1945 UNITED STATES PATENTS 2,624,652 Carlson Jan. 6, 1953 324,496 Stosch Aug 18J 1885 217261166 Greaves DeC- 6, 1955 

